1. Field of the Invention
This invention relates to wide-area lighting or display structures made up of a plurality of relatively small discrete light sources such as light emitting diodes (LEDs), corresponding to the lighting elements originally described in U.S. patent application Ser. No. 09/592,913, incorporated herein by reference, and in particular to various modifications and new applications of the lighting elements described in U.S. patent application Ser. No. 09/592,913.
The new applications include adaptation of the lighting elements described in U.S. patent application Ser. No. 09/592,913 to function as a conventional-type or stereoscopic color video monitor, a light bulb, or a flexible neon sign replacement element. In addition, the present patent application discloses various alternative constructions of the lighting element described in U.S. patent application Ser. No. 09/592,913, including combination of smaller elements into larger elements to provide a full color flat lighting, and variations in the manner in which the diffusive agent and reflective structures are arranged, including use of lenticular or reflective diffusers, and microprism sheets with varying light transmission properties as described in copending U.S. patent application Ser. Nos. 09/481,942, 09/538,731, and 09/559,177.
2. Description of Related Art
Light emitting diodes have a number of advantages over conventional lighting elements, including relatively low power consumption, the ability to emit light of different colors, and durability. However, because of the small size of LEDs, they cannot be used to provide wide area lighting or display elements or structures.
In parent application Ser. No. 09/592,913, it was proposed to combine the conventional LEDs into a new type of lighting element in which light from the individual LEDs is diffused through a microprism sheet to provide a lighting effect similar to that provided by a fluorescent light, and yet that is flexible and can therefore be formed into a wide variety of configurations, including tube-shaped structures capable of emulating a fluorescent light tube, without the relatively high power consumption of a conventional fluorescent light tube or the need for an electronic ballast.
The present application utilizes the principles of combining LEDs with diffusers and/or a reflector to provide uniform light emission in the manner of a fluorescent light tube or panel, but extends the concept to (i) the construction of diverse light sources such as flat panel video monitors, light bulbs, and so forth, (ii) the addition of multiple colors where appropriate, (iii) use of different types of diffusive agents, including use of lenticular or reflective diffusers, and microprism sheets with varying light transmission properties as described in the above-cited copending U.S. patent application Ser. Nos. 09/481,942, 09/538,731, and 09/559,177.
The use of microprism sheets having light diffusing properties is of course well-known for purposes such as glare reduction overlays, rear or front projection screens, or light-diffusion screens of the type interposed between the back of a liquid crystal diode (LCD) screen and a light source. Examples of prior microprism arrangements involving light diffusion are disclosed, for example, in U.S. Pat. No. 3,718,078 (Plummer), U.S. Pat. No. 3,902,787 (Sherlock), U.S. Pat. No. 4,309,073 (Nishimura et al.), and U.S. Pat. No. 5,837,346 (Langille et al.).
In general, however, in contrast to the present invention, the microprism sheet arrangements disclosed in these references use the diffusion properties to smooth out irregularities or hot spots with respect to light or images that are spread out over a relatively large area, as opposed to providing more uniform transmission of light sources intentionally combined together to provide a large display or light source.
Additional examples of microprism sheets which may be provided with light diffusing properties are disclosed in copending U.S. patent application Ser. No. 09/481,942, filed Jan. 13, 2000, which discloses a number of microprism sheet treatment arrangements, in the context of privacy screens, interlacing arrangements and light separating arrangements, but not specifically for use in lighting elements.
One prior lighting arrangement involving use of microprism sheets in connection with "point sources" such as LEDs is disclosed in U.S. Pat. No. 5,835,661 (Tai et al.). However, the system disclosed in this patent seeks "the conversion of light from a point-like light source to a linear or planar light beam having a sufficiently uniform distribution of light" by employing a light pipe combined with microprism structures which are used to divert light out of the light pipe over an extended surface. The lighting arrangement disclosed in U.S. Pat. No. 5,835,661 is said to be useable in displays, road signs, medical research equipment, instrument meters or jewelry, light pictures or art work, or for surgical or dental lighting, but nevertheless is disadvantageous because of its relative complexity and because the lighting elements disclosed in the patent is are limited to rigid rather than flexible structures. The present invention is intended to be suitable for use not only in the applications listed in U.S. Pat. No. 5,835,661, but also in a variety of additional lighting applications requiring more flexible, low power, wide area lighting.
Finally, those skilled in the art will note that the use of diffusive agents such as microprism sheets to diffuse light emitted by the LEDs permits the light to be combined in a more uniform manner than is possible with conventional diffusers, which do not have the selective light bending properties of a microprism sheet. On the other hand, however, it is also within the scope of the present invention to use a conventional diffuser in connection with the lighting elements since the prior art does not show use of multiple discrete lighting elements and a diffuser as a video monitor, light bulb, or light tube, regardless of the type of diffuser.